$(function() {
	var $backToTopTxt = "返回顶部", $backToTopEle = $('<div class="backToTop"></div>').appendTo($("body"))
	.text($backToTopTxt).attr("title", $backToTopTxt).click(function() {
	 $("html, body").animate({ scrollTop: 0 }, 120);
	}), $backToTopFun = function() {
	var st = $(document).scrollTop(), winh = $(window).height();
	(st > 0)? $backToTopEle.show(): $backToTopEle.hide();   
	//IE6下的定位
	if (!window.XMLHttpRequest) {
	$backToTopEle.css("top", st + winh - 166);   
	}
	};
	$(window).bind("scroll", $backToTopFun);
	$(function() { $backToTopFun(); });
})();